POZZOLANE AND SLAGS
Tlus quantity usually varies between i and 2 grams and is greater with
the better pozzolane.
3. Granularity and Fineness.óWith poraolane in the natural granular
condition, the degree of granularity is determined by using a series of sieves
with meshes measuring 5, 4, 3, 2, 1-5, i and 0-5 mm., 2 grams of material
being taken and the results expressed as percentages (of the total weight)
not passing through each sieve. With powdered poz/olanu, however,
the fineness of grinding is determined in the way indicated later for
This procedure, and also the ones described under 4, 5, o and 7, are those
prescribed in the Official Italinn .Ht'.frithitioiis and Conditions, approved by the
decree of the Minister of Public, Works, June 13, ion.
4. Specific Gravity.-......The specific gravity (absolute density) is deter-
mined on the powdered material, dried and passed through a, sieve of 900
meshes per sq. cm., by the methods indicated later for cements.
5. Apparent Density.-.....This is the weight of i hire of the material
poured without compression. With granular poiaolunc it is determined
after the latter has been dried and passed through a sieve with round orifices
3 mm. in diameter, the same apparatus and procedure being used as with
cements, excepting thai: the plate in the funnel has apertures 3 mm, instead
of 2 mm. in diameter. With powdered poy.y.olane, however, the apparent
density is determined exactly as with cements. The result is expressed
in grains per litre (or kilos per cub. in.).
6. Setting Test.- The procedure is different for granular or powdered
In the former case the po///.olaua should be previously dried in the oven
until of practically constant weight and then passed through a sieve with
circular holes 3 mm. in diameter. Common lime (with at least 95% CaO)
is hydnited by sprinkling it with water, being afterwards left for a fortnight
in a moist place and sieved to remove uneombined or inert particles. A
normal morltrr is then prepared from i part, of the powdered slaked lime
and 3 parts of the poy,y,olana prepared as above ; tin* manipulation is carried
out at a, temperature of 15- 20" on a. marble slab by means of a trowel, the
components being mixed at first dry and then with ordinary water, this
being gradually added until a homogeneous, plastic mass is obtained which
agglomerates under the pressure of the hand.
This mortar is used to (ill two /inc. plate cylindrical moulds, 10 cm, in
diameter and 5 cm, in height, which are kept in a moist atmosphere, the
setting tests being commenced after .|H hours and repealed every 24 hours.
In this test use is made of a Vieat needle similar to that described later for
cements but with a total weight: of i kilo and of rather different dimensions :
the. point of the needle is somewhat conical, the length being ,|o mm., and
the. diameter 3-2 mm. at the, base and H>(> mm. at the apex. The needle
is allowed to Call from a height of 30 mm., and hardening is considered to
begin when the needle does not penetrate more than 7 mm. Into the mortar.
At this point, one of the mortars is placed in water and the other kept in
the moist, chamber, the periodical tests being continued on both and thehe proportions